Wireless telegraph receiver



Dec. 11, 1928. 1,694,646

c. s. FRANKLIN WIRELESS TELEGRAPH RECEIVER Original Filed June 25, 1919Patented Dec. 11,1928.

A I UNITED STATES PATENT orrlcs,

CHARLES SAMUEL FRANKLIN, LONDON, ENGLAND, ASSIGNOR, BY MESNE ASSIGN-MENTS, TO RADIO CORPORATION OF AMERICA, AOORPORATION OF DELAWARE.

WIRELESS TELEGRAPH RECEIVER:

Application filed June 25, 1919, Serial No. 306,608, and in Grpat'Britain June 28, 1928. Renewed October This invention relates toimproved circuits for wireless telegraph receivers, and is particularlyapplicable for receivers for waves of a few metres. g

In receivers employing thermionic devices it is usual to connect thesecondary circuit of the receiving transformer between the grid andfilament of a valve of the three electrode type, or between the anodeand filament of l a valve of the two electrode type As the capacity atthe filament end of the secondary is large (owing to the batteries,accessories and leads required) compared with the capacity at the gridor anode end, the variations of potential produced across the'secondaryby the received waves cause a" greater variation in the potential of thegrid 01' anode relatively to the surroundings than in the potential ofthe filament.

It has now been found that by arranging the circuit so that thepotential of the filament rather than the potential of the grid oran'ode is varied relatively to its surroundings, a valve receiver ismade many times more sensitive for short waves.

To obtain this efiect it is necessary so to arrange the circuit that thecapacity at the filament endof the secondary is a mlnimum. This may beefiected by connecting the lighting battery to the filamentthrough longchok: ing coils; the capacity of the lighting bat tery and accessoriesdoes not then materially affect the capacity at the filament end of thesecondary. It is preferred, however, to cause 5 the secondary directlyto affect the potential of the filament by connecting the-seco'ndarydirectly in theleads to the filament. As two wires must be employedbetween the battery and the filament, the secondary is 4 wound with twowires laid together on the same former, the two wires being connected atone end of the coil to the filament and at the other end, preferablythrough long choking coils, to the heating battery and ac- J cessories.A tuning condenser is connected in parallel with the secondary; this ispreferably arranged in two equal parts each connected in parallel withone of the secondary wires. The telephone or indicator may be connectedin series with an adjustable battery.

and choking coil between the anode and the --filament lighting battery.

The invention 15 illustrated by the accompanymg diagram, in'which 1 is avalve having a filament 2 and an anode 3. 4 is a secondary coupled to aprimary-5 in an aerial circuit and consisting of'two wires woundtogether on" a former and connected at one'end to the filament 2 and totuning condensers 6, 7, and at the other end to choke coils 8, 9, to thecondensers 6, 7, and to fixed condensers 10, 11. The coils 8, 9,.areconnected at one end to a resistance 12 and a battery 13 which heatsthe filament 2, and at the other end to the condensers 6, 7. 1 1 is athird choke coil connected at one end to the condensers 10, 11, and tothe anode 3, and at the other end through the primary 15 of atransformer of which the secondary 16 is connected to a telephone 17, tothe positive of a battery 18 of adjustable voltage, the negative ofwhich is connected to the heating battery 13. The secondary circuitcomprising the-coil f and condensers 6 and 7, is tuned to the wavereceived. 1 The choking coils 8, 9, 14, are not essential, but they areparticularly useful in the case of short waves in preventing theoscillations picked up by the telephone and battery wires 30 fromaffecting the secondary circuit. It will be noticed hat thefilament 2 iscon-' nected solely tothe secondary circuit, while the anode 3isconnected'to the coils 8, 9 and 14, and the battery leads besidesbeing con .nected to the secondary; consequently the capacity of 3relatively to its surroundings will be greater than that of 2. 7 Itfollows that when anydiiference-of potential is produced between 2 and 3by the secondary, the v'ariation of potential of 2 relative. to itssurroundings will be greater-than that of 3.

What I claim is h 1. 'A circuit comprising a transformer having a coilconsisting'of two conductors wound together and insulated from eachother, a thermionic valve having a filament and a. 7 cold electrode,each conductorof the coil being connected at one end-of the coil toopposite leads respectively of the filament, and a battery connected tothe filament through said conductors. p v

2. A circuit comprising "a transformer, a thermionic valve hav' g afilament and a cold electrode connected t rough a circuit including acoil of the transformer and a condenser,

a source of space current for said valve, a source of current forheating the filament, andf means between the sources of current and thefilament for neutralizing the capacity effect of said sources of currentand their associated connections on the filament end of the coilwhereby: the variation of potential at said end, when oscillations areimpressed on the coil,

is increased. 7 1

3. A circuit comprising a transformer, a thermionic valve having afilament and a cold in electrode coupled by a circuit whichincludes thetransformer coil and another circuit con-' nectingjsaid filament and"cold electrode and containing a source of current, a. second source ofcurrent for heating the filament and in- 1 ductances between the sourcesof current and filament for neutralizing capacity effect of said sourcesof current and their associated connections on the filament end of thecoil whereby the potential at said end varies be tween a minimum and amaximum relative to 3 its surroundings when oscillations are impressedon the secondary. 4. A circuit comprising a first inductance, athermionic valvevhaving a filament and a cold electrode connected toeach other through a circuit including the first inductance and throughanother circuit containing a source" of current, a second source ofcurrent for heating the filament, and a second inductance ,be tween thesecond source of current and the filament.

5. A circuit comprising a transformer hav-.

ing a coil consisting of two conductors wound together and insulatedfrom each other, a

thermionic valve having a. filament and a cold electrode, each conductorof the coil being connected at one end of the coil to opposite leads resctively of the filament, the other ends of t i e conductors beingseparately 40 capac'itively coupled to the cold electrode, and

attery connected-to the filament through 2 i the coil. A

i 6. A circuit comprising a transformer having a coil consistin of twoconductors wound together and insu ated from each other, a thermionicvalve having a filament and a cold electrode, each-conductor of the coilbeingconnected at one end of the coil to oppositeI leads respectivel ofthe filament, the other ends of the con uctors being separatelycapacitively coupled to the cold electrode, a battery connected to thefilament through leads containing inductance, a circuit connecting thefilament and cold electrode containing a 65 battery and inductances inthe connections of said circuit between the filament and cold electrode.

7 A circuit comprising a transformer having a coil consisting of twoinductances and insulated from each other, a thermionic valve having afilament and a cold electrode, each "inductance of the coil beingconnected at one end of the coil to opposite leads respectively of thefilament, the other ends of-the inductances being connected in circuitwith the cold electrode, and aJbat-tery for heating the filamentconnect-ed thereto through the inductances.

8. A circuit comprising a transformer havconductor of the coil beingconnected at one end of the coil to opposite leads respectively of thefilament and the other ends of the conductors connected to the coldelectrode through a pair of condensers, and a battery for'heating thefilament connected thereto.

9. The combination with an electron emission tube filament which is notat the radio frequency potential of the general surroundingsyand afilament heating source which is at substantially the radio frequencypotential of the general surroundings of a pair of impedances arrangedin series with respect to the filament heating current, and in parallelwith respect to the radio frequency current for overcoming the potentialdifference between the source and the filament. I

l().- In combination, an electron emission tube having a filament whichis not at the potential of the general surroundings, a ra- (llOfrequency circuit assoclated therewith, a

sourceof filament heating current which is radio frequencycircuit inparallel for the radio frequency current and in series for the filamentheating current, said impedances being of proper magnitude to overcomethe potential diflerence between the filament and the source.

11. An electron tube circuit comprising an electron emission tube havinga filament which is not at the potential of the general surroundings andat least one other electrode, a radio frequency circuit including acoupling inductance connected between said electrodes, a source offilament heating current, said source being at substantially thepotential of the general surroundings, and means connecting said sourceto said filament comprising the coupling inductance and anotherimpedance in arallel therewith for overcoming the di erence'in potentialbetween the filament and the general surroundings.

12. An electron tube circuit c'om rising an electron emission tubehaving a lament. which is not atthe potential of the generalsurroundings and at least one other electrode, a radio frequency circuitcomprising a tuning inductance and a tuning condenser connected betweensaid electrodes, a source of filament heating current, said source beingat substantially the potential of the general surroundings, and meansconnecting said source to said filament comprising the tuning inductanceand another impedance in parallel therewith for overcoming thedifference in potential between the filament and the generalsurroundings.

13. An electron tube circuit comprising an electron emission tube havinga filament which is not at the potential of the general surroundings andat least one other'electrode, a radio frequency circuit including animpedance connected between said electrodes, a source of electricalenergy for heating said filament, saidsource being at'substantially thepotential of the general surroundings, aiml a pair of leads connectingsaid source to the filament, each lead including a portion of thesaid-impedance in order to overcome thepotential difference between thefilament and the source.

14.. In combination, an electron emission tube having a hot and a coldelectrode, a radio frequency circuitfconnected therebetween, a pair ofinductances in said circuit arranged in parallel with respect to theradio freuency current, asource of. energy for heating t e hotelectrode, and means connecting the 'hot electrode and the sourcecomprising said pair of inductances arranged in series wlth respect tocurrent from the source.

15. In combination, an electron emission tube having a hot cathode andan anode, a radio frequency circuit therebetween, a source of cathodeheating current, said source 'being series with respect to the filamentheating,

current for overcoming the potential differencebetween the source andthe filament, whereby the radio frequency potential fluctuations takeplace substantially on the cathode. r

16. In combination, an electron emission tube-having a hot cathode whichis'not at the radio frequency potential of the general surroundings, andan anode which is at substantially the radio frequency potential of thegeneral surroundings, a radio frequency circuit therebetween, a sourceof cathode heating current which is at substantially the potential ofthe general surroundings, and a pair of radio frequency impedances insaid circuit and arranged in series with respect to the filament heatingcurrent and in parallel with respect to theradio frequency current forovercoming the otential difference between the source and t e filament.I

In testimony that I claim the foregoing as my invention I have signed myname this 13th day of J one, 1919.

o CHARLES SAMUEL FRANKLIN.

